Hong Kong's MTR runs on 211 km of rail with 150 stations, including 82 underground stations and 68 light rail stops. 3.76 million people use it on an average weekday.
Fare: .85 cents with contactless Octopus card
Hours: 6 AM to 1 AM
If Moscow's Metro is a nostalgic doyenne, the Hong Kong MTR is something like an obsessively nerdy accountant, known for its reliability, cleanliness and to-the-second timeliness (a late rush-hour train reportedly made headlines a few years ago). But its real distinction is as one of the few subway systems to turn a profit. The privately-owned MTR Corporation rents out shop space in subway stations and owns the real estate along its tracks, which it develops to build revenue, further enhancing the riding experience, and gaining new riders. Singapore's MRT relies upon a similar model, also to excellent effect.
The MTR's contact-less Octopus card has become a sine qua non in Hong Kong, where it can be used not only on subways but to make purchases at shops around town. In 2006, the company broke the state monopoly in China to construct and manage Beijing's Line 4 subway, and in June won the bid to run the metropolitan railway network in Melbourne, Australia, taking over from Melbourne's existing network operator, the French-owned firm Connex.
Flickr: mikeleeorg; wyliepoon; spavaai